P700 - 799

P 722 - Load-bearing capacity of anchor plates with headed stud anchors in bar-shaped components Anchor plates with welded-on headed studs in narrow concrete components such as foundations or columns are currently designed with the help of structural engineering approvals. A very conservative calculation method is used here, which only insufficiently recognises the influence of the existing stirrup reinforcement on the load-bearing capacity of the anchor plates. Building on the research results of an earlier DASt/AiF research project on anchor plates in wall-like components, connections with rigid base plates and anchor plates with welded head bolt dowels in column-like concrete structures were investigated as part of the research project, taking into account existing stirrup reinforcement, in order to determine a simple and economical design model based on the component method for these connections. A test programme with 19 tests was carried out to investigate the load-bearing behaviour of the connections. The parameters of concrete quality, stirrup reinforcement and edge distance of the head bolt dowels were varied. The parameters were selected so that they corresponded to the minimum requirements to be met. With the help of a numerical model, which was verified in the tests carried out, further FEM analyses were carried out on the load-bearing behaviour of the embedded anchor plates and the load-bearing behaviour of the concrete and the existing reinforcement. The knowledge gained from these analyses served as the basis for the development of the mechanical model. Based on an initial component model for anchor plates without edge distances, the model for anchor plates close to the edge could be further developed, taking into account the calculation approaches of the fastening technology. The typical failure modes of headed stud anchors close to the edge are taken into account by individual components. The load-bearing behaviour of the anchor plates is well represented by the proposed model and remains on the safe side overall. Further development of the model and adaptation to future research and standardisation results is possible thanks to the modular structure of the component method. This means that the model can be adapted for other fastening elements such as undercut anchors or chemical fastening systems and other installation situations by replacing individual components or inserting new components. Compared to existing calculation options, an economical design model was created for the anchor plates in the analysed parameter range. The possibility of taking into account existing reinforcement for the back-anchoring of shear stud dowels, even close to the edge, allows a realistic calculation to be carried out and a very advantageous and economical design of the connections to be achieved. Authors: U. Kuhlmann, M. Rybinski Publication: 2007

P 721 - Slit profiling of thin sheets - Production and further processing As part of current endeavours to advance the development and application of lightweight construction strategies, the main objective is to achieve increasingly higher component strengths with decreasing material volumes and to be able to cover critical component areas with weight-reducing materials in the future. In addition to the development of high-strength and ultra-high-strength materials as part of lightweight material construction, efforts are also being made in lightweight mould construction to reduce the sheet thickness while maintaining the same component properties. However, one problem with weight reduction is component failure due to buckling or buckling caused by instabilities. An effective design element for shifting this instability limit towards higher loads is the introduction of bifurcations. With the help of the gap profiling process, a forming process has been developed that allows branches to be realised on the strip edge of sheet metal, which was previously only possible by doubling material within die bending or roll forming processes. In addition to the effect of increased profile rigidity, it is possible to utilise branches for new, load-adapted joining strategies. Furthermore, the downstream processing of branched profiles opens up a wide range of new functional profile applications. As part of the activities of the "Rolling and gap profiling" working group, the process development of gap profiling was advanced through the realisation of a new type of tool concept. A hydrostatic compressive stress state is induced in the workpiece through a targeted arrangement of nip and auxiliary rollers, which increases the material's ability to change shape and leads to the formation of branches, so-called flanges, on the edge of the sheet metal strip. The results obtained during development were presented using the example of two micro-alloyed fine-grained steels. It was possible to produce branches with a span of approx. 30 mm. The splitting profiles have a macroscopically crack-free surface as well as a significant hardening gradient, starting from the surface facing the splitting rollers. Based on this, it is possible to further process the slit profiles using forming technology. Die bending and roll forming processes can be used to create functional multi-chamber profiles which, in addition to increased rigidity, buckling and buckling stability, also offer the possibility of functional integration. As part of the working group's activities, the roll-forming moulding of gap profiles into a single-chamber profile was investigated in particular. Conventional tools for designing roll forming processes cannot be used due to the fact that branches cannot be modelled. Instead, the process was modelled and analysed using FE systems. Furthermore, aspects of tool design and layout were investigated that arise when profiling branched semi-finished products due to the occurrence of undercuts. The single-chamber profile realised as part of the working group demonstrates the possibilities opened up by a process chain consisting of gap and roll forming: The process limits of slit profiling allow the geometry of the semi-finished product slit profile for subsequent forming to be varied over a wide range, enabling the production of thin-walled, integrally branched multi-chamber profiles of variable geometry with free flanges. Prospective opportunities therefore lie in particular in the realisation of innovative, multifunctional products with advantages that affect both their properties and the production possibilities and costs. The activities of the Rolling and Gap Profiling Working Group are being continued as part of the transfer project "Mastering tolerance fields in gap and roll profiling" within the SFB 666. The main objectives of the research projects are to analyse accuracy and tolerances in order to derive industrially feasible product classes and, based on this, corresponding strategies for the process-reliable design of a continuous process chain for slitting and roll forming. Authors: P. Groche, D. Vucic, P. Beiter, R. Salomon Publication: 2011

P 717 - Protection of vehicle occupants through improved effectiveness of steel crash barriers The aim of the research project is to improve the level of protection for vehicle occupants in the event of an accident between a vehicle and a road barrier. Through the interdisciplinary co-operation between vehicle technology (ika) and steel construction (Stb), it is possible to investigate how the vehicle accelerations occurring in a car collision are related to the expected risk of injury to the occupants. The injuries resulting from an accident can then be reduced by means of a suitable design. The evaluation of the current classification criteria used for impact severity in accordance with EN 1317 is at the centre of the research project. While correlation studies on injury severity already exist for the HIC criterion used in the automotive industry (evaluation of accelerations at the (dummy) head), comparable studies are not known for the main parameter used in EN 1317, ASI (evaluation of accelerations at the vehicle's centre of gravity). Therefore, both simulations and sled tests are carried out here with various dummy models (US-SID and Hybrid II) with and without vehicle bodywork. A multi-body dynamics programme and a finite element programme are used for the simulations. To improve the prediction quality, these are extended by a more precise representation of the vehicle-road interaction and by the implementation of an occupant dummy including belt system. Compared to real crash tests, the good reproducibility of both the simulation results and the sled tests is crucial. The experimental investigations in the sled test show a polynomial (or exponential) correlation between the ASI and the HIC with a high coefficient of determination. It is significant that all sled tests with a configuration for a rigid restraint system lead to a breakage of the side disc through the dummy head. Overall, the results of the tests and the simulations demonstrate the significantly higher occupant load in the event of a vehicle impact with comparatively rigid restraint systems compared to the more flexible steel restraint systems. The simulations also provide valuable preliminary work for the reinforcement of the vehicle restraint system "Simple distance guardrail with 2.0 metre post spacing (EDSP 2.0)" used as standard to date for the area of application with the required containment level H2 according to EN 1317. In further impact simulations, accompanied by drop tower tests, it can also be shown that the use of higher-strength steel can increase the resource efficiency and thus the sustainability of steel crash barriers. The IGF project 14823 N of FOSTA - Forschungsvereinigung Stahlanwendung e. V., Düsseldorf, was carried out at the Chair and Institute for Steel Construction and Light Metal Construction, RWTH Aachen University and the Institute for Motor Vehicles Aachen, RWTH Aachen University and was funded by the Federal Ministry of Economics and Technology via the AiF as part of the programme for the promotion of joint industrial research and development (IGF) on the basis of a resolution of the German Bundestag. Authors: M. Feldmann, C. Kammel, F. Möller, A. Geßler, D. Neuenhaus, H. Wallentowitz, S. Kurtenbach Publication: 2011

P 715 - Verification and correction of reduction coefficients according to Eurocode 3 for hollow section connections made of materials with yield strengths between 355 MPa and 690 Mpa The design of hollow section connections made of high-strength fine-grain structural steel in accordance with DIN EN 1993-1-8 is carried out in the same way as for normal-strength general structural steel with a maximum yield strength of 355 MPa and additional consideration of a reduction factor. For structural steels with a yield strength of 355 < fy < 460 MPa, the design values of the tensile strength must be reduced by α = 0.9 and for structural steels with a yield strength of 460 < fy < 700 MPa by α = 0.8. As part of this research project, these reduction factors were checked and the influence of the geometric parameters 2γ (chord slenderness), τ (wall thickness ratio) and β (width ratio) on the reduction was investigated. The experimental investigations were carried out on X-nodes made of hollow sections with a circular cross-section (KHP) made of fine-grained structural steel S460 and S690. The specimens were subjected to tension and compression as well as bending in the joint plane (IPB). The geometric influences on the reduction coefficient were investigated using FE analyses. The two failure modes of chord plasticising and punching were considered. The node load-bearing capacities for belt plasticising were determined using the 3% deformation criterion. A separate numerical model was developed for the punching shear failure mode, which can be used to simulate the formation of cracks in the belt cross-section. However, complex experimental investigations are required to determine the input parameters of this model, e.g. to take into account the multi-axiality of the tension, but these could not be carried out as part of this project. It was therefore not possible to check the reduction factors for the failure case of punching shear. The results of the experimental investigations to date indicate that it may be possible to dispense with joint verifications if the belt slenderness and the wall thickness ratio do not exceed certain limit values. The verification of the connection would then already be included in the verifications of DIN EN 1993-1-1. The current lower limit for chord slenderness (d0/t0 ≥ 10) for the application of EN 1993-1-8 could then also be omitted. However, further investigations are required for this. As the statistical analyses are only of limited significance due to the small number of test data, no final recommendation for a change in the coefficients can currently be made on the basis of the results obtained. However, it was confirmed that the reduction coefficients according to DIN EN 1993-1-8 and DIN EN 1993-1-12 are always on the safe side for all analysed cross-sections of cross-section classes 1 and 2. The research project was carried out by the Research Centre for Steel, Wood and Stone at the Karlsruhe Institute of Technology (KIT) and the Laboratory for Steel and Light Metal Construction at Munich University of Applied Sciences, Faculty of Civil Engineering, with technical support and financial assistance from the Forschungsvereinigung Stahlanwendung e. V., Düsseldorf, with funds from the Stiftung Stahlanwendungsforschung, Essen. Authors: R. Puthli, S. Herion, O. Fleischer, Ö. Bucak, I. Engelhardt, A. Fischl Publication: 2014

In research project P714, building on the fundamental investigations of project P611 on the weldability of various coated sheet steel grades, non-vacuum electron beam welding (NVEBW) was qualified for use in sheet steel processing, particularly in car body production, under near-industrial conditions. The higher-strength, galvanised steel sheet grades HX420LAD+Z, HXT600X+Z, HXT700T+Z and BTR165 with sheet thicknesses between 0.8 and 2 mm were the focus of the investigations. Firstly, the process tolerances for NVEBW were determined as a function of different seam geometries, steel sheet grades and sheet thicknesses. In particular, the gap bridging capability, the tolerance to positional deviations and the edge offset were analysed. A particularly good gap-bridging capability was demonstrated for the NVEB welding of lap seams and flanged seams. In the case of I-seams, the gap bridgeability is highly dependent on the material. The process tolerances determined with regard to positional deviation and edge misalignment can be rated as large. The use of filler materials can further improve the gap bridging capability. In the tests with oblique beam incidence with an angle of inclination of 15°, a reduction in the edge notch depth was observed for the materials HXT600X+Z and HXT700T+Z at a welding speed of 12 m/min. In the NVEBW of beaded seams made of HXT600X+Z and HXT700T+Z, a reduction in the humping and the edge notch depth, i.e. an overall stabilisation of the weld fusion, was observed with a beam inclination angle of 15°. Fatigue strength tests on NDEB-welded H-specimens for the four materials investigated show similar load cycle levels with comparable force amplitudes. The suitability of NVEB as a joining technology has been conclusively demonstrated by means of component welds and crash tests. The crash properties of NVEB-welded and spot-welded bumpers from Benteler Automobiltechnik GmbH have been tested. The crash tests show comparably good crash properties for both the original bumpers and the NVEB-welded bumpers. In addition to the cycle time, the vehicle weight is particularly important with regard to CO2 emissions and fuel consumption. In this context, the weight of the NVEBW bumper was reduced from 4.95 kg to 4.30 kg by adapting the joint geometry to the welding process. The tests carried out confirm the excellent suitability of the NVEBW for processing coated steel sheet in car body construction. This is not only due to economic advantages such as a high welding speed and a high degree of efficiency. The investigations also show the advantages necessary for practical use, such as high process reliability and the flexibility of the process. FOSTA Research Association for Steel Application e. V. Publication: 2012 Authors: Dr.-Ing. K. Lau, Dipl.-Ing. R. Konya, Dr.-Ing. T. Hassel

P 713 - Production of tubes with flexible wall thickness by roll forming of strip-rolled pre-material In today's commercially available tailored tubes, the diameter and possibly also the wall thickness vary along the longitudinal axis of the tube. This project was the first to demonstrate that the combination of strip profile rolling and roll forming can be used to economically produce tubes with varying wall thicknesses in the circumferential direction in a continuous process. Even as a straight tube, this makes it possible to tap into previously unrealised lightweight construction potential. In addition, it was shown that this new class of tubes can be further processed into geometrically sophisticated lightweight structures after annealing treatment, e.g. by hydroforming. The basis for the successful realisation of the demonstrator tubes was created through extensive simulation studies of the process chain, so that validated simulation models are now also available for the development of further profile variants. Based on a consideration of the area moment of inertia, three cross-sections for circular tubes with varying wall thicknesses were determined, which have a particularly favourable ratio of bending stiffness to weight. For the roll forming of the pipe geometry selected as a demonstrator, a 186 mm wide strip is required as the starting material, the thickness of which had to be reduced from 2.5 mm to 1.5 mm in the centre area over a width of approx. 50 mm by means of strip profile rolling. Based on the basic principles of strip profile rolling known at the beginning of the project, the influences of the process, geometry and material parameters on the formation of the cross-section were first investigated in a comprehensive parameter study with numerical simulation (FEM) and an optimised roller geometry and rolling strategy was developed. This rolling strategy was implemented on an industrial scale on a roll forming line, on which around 120 metres of Tailor Rolled Strip (TRS) were produced in three passes with a total of 25 passes for further processing. The various conceivable forming strategies for roll forming the TRS were also evaluated and optimised with the help of extensive FEM simulations. The pre-hardening from the strip profile rolling was taken into account on the basis of a measured hardness distribution and the entire moulding process was mapped as an FEM model. Based on this preliminary work, the pipes were successfully moulded and closed using HF welding, whereby the roundness and shape deviations were slightly higher than those of a reference pipe with a constant wall thickness. Bursting tests using hydroforming with free expansion showed that the tailored tubes produced in this way can be formed by hydroforming after recrystallising annealing and even exhibit slightly better formability than a reference tube in which the difference in wall thickness was produced by milling. The process combination of strip profile rolling with subsequent roll forming can be carried out on highly productive roll forming lines. This means that a high level of cost-effectiveness can be expected in particular if as few passes as possible are required to produce the TRS. This is always the case when the TRS has one or more narrow grooves. Wide or particularly deep grooves, on the other hand, are considered costly. FOSTA Research Association for Steel Application e. V. Publication: 2010 Authors: Prof. Dr.-Ing. P. Groche, Dipl.-Ing. M. Mirtsch, Prof. Dr.-Ing. G. Hirt

P 710 - Development of a technology for controlled heat conduction in metal active gas welding of structural components The effective utilisation of the newly developed high-strength steels HCT690T+Z100 (1.0947), HCT780X+Z100 (1.0943), HDT1200M (1.0965) and 22MnB5+AS (1.5528) requires suitable joining technologies. The aim of this work was to transfer the properties of the base materials to the joining properties. To this end, fusion welding processes with controlled energy control were investigated in combination with specially developed filler materials. The compositions of the filler materials are adjusted in such a way that they largely correspond to the composition of the base materials, taking the welding technology into account. In addition, comparative analyses were carried out between the four newly developed cored wires and three commercially available solid wires. Seamless cored wires were used in the investigations. They were designed as metal powder types for use under mixed gas. They are ideally suited for fully mechanical and automated processes. The wires were processed using modern welding technology equipment. Both direct current and alternating current machines were used. With the exception of one solid wire, it was possible to weld all filler materials reproducibly under alternating current conditions. By balancing positive and negative polarity, alternating current technology offers excellent possibilities for controlling the energy input into the base material over a wide range. This ensures a basis for defined energy control. The possibilities of process-integrated energy management were also assessed. The newly developed short-time heat treatment is particularly suitable for joints on the HCT690T+Z100. The applicability of two different systems was presented and their impact on the joint properties was demonstrated. A significant reduction in the hardness of the weld metal and the heat-affected zone was demonstrated. This result was confirmed by the realised impact tensile tests. The sample was only destroyed at a significantly higher energy than was recorded for untreated samples. The energy supplied as a result of the bonding process was recorded using highly accurate current-voltage-time measurements. Systematic measurements of the cooling times were also carried out. Only the combination of filler material and processing technology made it possible to produce joints that largely corresponded to the base material properties. The reactions to quasi-static, cyclic and impact loading of the manufactured samples served as assessment criteria. Corrosive and metallographic tests were also used. All test results were summarised in a database. The user is guided by a menu from the task to the welding instruction. In addition, information is provided on the joint properties, the fracture position, the joining parameters and the results of the metallographic tests. The work contains a welding time-temperature transformation diagram for HCT780X+Z100 (1.0943) - on the basis of which the theoretical considerations for assessing the heat-affected zone are based. The applicability of commercially available software packages for AC processes can also be established with good agreement. FOSTA - Forschungsvereinigung Stahlanwendung e. V. Publication: 2009 Authors: Dipl.-Ing. J. Vester, Dr.- Ing. H. Heinemann, Dipl.-lng.(FH) T. Ebersbach, Dipl.-Ing. A. Panthel,

P 709 - Press hardening of Tailor Welded Blanks The production technology of press hardening or mould hardening is nowadays a standard process in the automotive industry for the realisation of safety-relevant structural components. In the direct press hardening process, the boron-manganese steel 22MnB5 (1.5528) is hot-formed and tempered in a single process step after prior austenitisation. This makes it possible to produce geometrically complex components with a tensile strength of over 1500 MPa. The aim of the research project was to fundamentally investigate the technology of press hardening of laser-welded Tailor Welded Blanks (TWB) with regard to the realisation of functionally optimised structural components with customised mechanical properties. In this context, the first step was to select a suitable joining partner for the press-hardenable boron-manganese steel 22MnB5 on the basis of its transformation and deformation behaviour under near-process conditions. With regard to the development of a process control strategy for the press hardening of TWBs using the finite element simulation method, a comprehensive characterisation and description of the mechanical properties of the partner material and the weld seam as well as the analysis of the effect of the position of the weld seam in the initial blank on the forming behaviour of laser-welded Tailor Welded Blanks under near-process conditions represented a major focus of the project. As part of the research project, the micro-alloyed steel material HX340LAD+AS150 (1.0933) was selected as a suitable partner material based on the results of the experimental investigations. After mould hardening, this covers both the desired strength range for the yield strength Rp0.2 between 350 and 500 MPa and for the tensile strength Rm between 500 and 650 MPa and also meets the target value corridor for the residual elongation at break of A50 > 13%. Investigations into the plastic forming behaviour of the micro-alloyed steel at elevated temperatures have shown that it is characterised by a noticeable temperature and strain rate dependence and has comparable forming limits of approximately δ1 = 0.4 for the plane strain range as the boron-manganese steel 22MnB5. Hardness measurements and metallographic investigations in the transverse direction across the weld seam have shown that the Al/Si coating leads to the formation of hard and brittle intermetallic phases in the seam area both in the initial and hardened state. No effects of the Al/Si coating on the moulding capacity after hardening could be determined in the experiments. FE-based and experimental investigations into the forming behaviour of press-hardenable Tailor Welded Blanks using so-called mini-B-pillar geometries have shown that no crack initiation could be detected in the seam area for any of the weld seam layers considered, even if the weld seam runs directly through the crack-critical area. The validation of the results under near-series conditions was carried out by press hardening laser-welded Tailor Welded Blank B-pillars at Audi AG in prototype construction. The research project was carried out at the Chair of Production Technology, Friedrich-Alexander University Erlangen-Nuremberg, with expert supervision and financial support from the Forschungsvereinigung Stahlanwendung e. V., Düsseldorf, with funds from the Stiftung Stahlanwendungsforschung, Essen. Authors: M. Merklein, M. Geiger, C. Kerausch, J. Lechler Publication: 2010

P 708 - Investigation of the structural stability of models for welding distortion simulation of steel materials Due to technological and economic advantages, welding with laser radiation has become established in industrial applications, especially for metallic materials. The use of welding simulation promotes process understanding and allows the consideration and minimisation of residual stress states and distortions in process planning. The aim of the project is to analyse the structural stability of the mathematical-physical equivalent models used in a variety of existing procedures for determining distortion in the welding of steel materials. In particular, the interaction of welding process and welding distortion simulation are at the centre of the considerations. The complexity of the interaction of the physical phenomena of the welding process on the machined component structure requires the identification of highly abstracted or reduced models with regard to the efficient use of simulation calculations in industrial applications. In order to support the user of the simulation in the selection of the applicable models for his specific application, the limits of validity of different reduced models for the calculation of the distortion and the temperature in the component are determined. The recommended choice of methods depends on the complexity of the component and the boundary conditions of the welding process. For this purpose, three components with very different sizes and structural behaviour are investigated: Gear wheel (compact component of medium size), sill (structural component from the automotive industry) and injection nozzle (micro component). Focussing the project on steel as a material makes it essential to consider the phase transitions in the solid phase. The relevance of different phase transition models for the quality of the calculated component distortion is being investigated for various steel materials typical of components. The industrial consortium accompanying the project supports the research centres in investigating the applicability of the existing simulation methods with regard to the properties of the materials under consideration and their possible integration into the structural simulation. To validate the simulation results, the analysis results and process parameters of real welding processes of the individual components are used. Authors: M. Zäh, T. Föckerer, A. Schober, W. Schulz, S. Pfeiffer Publication: 2010

P 704 - Investigations into the spot-weld bonding of high-strength sheet steel with new hot and cold-curing adhesive systems The combination of resistance spot welding with structural bonding offers a number of advantages over the individual processes, such as improved crash behaviour, higher joint strength under oscillating loads or improved corrosion protection of the joining zone. These are consistently utilised, particularly in the sheet metal industry. In recent years, developments in the automotive and automotive supply industry have led to the increased use of higher and high-strength steel materials in order to reduce the weight of vehicle bodies and increase their passive safety. and increase their passive safety. This research report presents results from investigations into the behaviour of high-strength and high-strength steel materials joined with current and new hot and cold-curing adhesive systems up to a strength of 1650 MPa. The influences of the welding process on the bonded joining zone and on the mechanical properties of the joint as well as the influences of the adhesives used on the joining process are discussed. The characterisation of the joints with regard to their mechanical properties and their corrosion properties provides the designer with a basis for the use of hot and cold-curing adhesive systems in combination with high-strength and high-strength steel materials. The IGF project 14476 N of the FOSTA-Forschungsvereinigung Stahlanwendung e. V., Düsseldorf, was funded by the Federal Ministry for Economic Affairs and Energy via the AiF as part of the programme for the promotion of joint industrial research (IGF) on the basis of a resolution of the German Bundestag. The project was carried out at the University of Paderborn, Laboratory for Materials and Joining Technology and at the SLV Munich branch of GSI GmbH. Authors: O. Hahn, H. Thommes, F. Zech, H. Cramer, T. Bschorr Publication: 2015

P 703 - Influence of inductive rapid curing on the property profile of bonded joints with regard to their crash behaviour The aim of the research project was to determine the influence of inductively accelerated adhesive pre-curing on the bond properties - especially under impact load. Inductively accelerated adhesive curing is becoming increasingly important in industrial manufacturing processes as it contributes to process time reduction. It enables a fast handling strength of bonded components immediately after bonding and increases the wash-out resistance of bonded seams in subsequent painting and cleaning processes. Four epoxy resin adhesives on a one- and two-component basis were used in the investigations, which were previously selected using impact test methods. Investigations into the reaction kinetic behaviour of the pure adhesive substance show that the curing behaviour of the adhesives depends on the heating rate. Analyses of the viscoelastic material behaviour show a change in the glass transition area and the adhesive stiffness for the induction-cured samples compared to conventionally oven-cured samples. The curing temperature and the heating rate were identified as process-critical parameters for inductive fast curing. Lower curing temperatures and heating rates were found to be advantageous. Further investigations on bonded joints, e.g. using the thick tensile shear test at increased slip rates, generally show lower maximum bearable shear stresses and fracture slip for inductively cured joints, so that inductive rapid curing leads to a reduction in the crash performance of the adhesives. Tests on bonded thin sheet metal joints with a low-alloy deep-drawing steel and a high-strength dual-phase steel also show that the effects of inductive rapid curing can be differentiated in the mechanical joint properties with different material strengths and surfaces. Impact tests were carried out on component-like T-joints in order to verify the comparability of the results from the previous investigations on simple test specimens. The results showed good agreement. With the knowledge gained in this project, both a quantitative and qualitative assessment of the crash behaviour of inductively pre-cured bonded joints can be made. The IGF project 14477 N of the FOSTA-Forschungsvereinigung Stahlanwendung e. V., Düsseldorf, was funded via the AiF as part of the programme for the promotion of joint industrial research (IGF) by the Federal Ministry for Economic Affairs and Energy on the basis of a resolution of the German Bundestag. The project was carried out at the Laboratory for Materials and Joining Technology, University of Paderborn. Authors: O. Hahn, H. C. Schmale Publication: 2015

P 702 - REFRESH - Extending the service life of existing and new welded steel structures In recent years, the significance of the service life of structures has gained in importance alongside the optimisation of the construction weight to reduce manufacturing costs. Highly stressed weld seam details are decisive for the service life of cyclically stressed welded steel structures. By increasing the fatigue strength of these notch details, the service life of the overall structure can be extended. This can be achieved by post-treatment of the weld seams using various methods. While grinding the weld seams is the only method used in the construction industry to date, other sectors are already successfully using strengthening methods such as shot peening. A large number of publications show the positive effect of specifically utilised weld post-treatment methods. Recent studies confirm the particular effect of higher-frequency hammering processes. A prerequisite for the widespread introduction of service life-extending measures, particularly in the construction industry, is that, in addition to the pure application of methods for extending the service life of existing and new steel structures, methods for calculating and quantifying the achievable effects as well as corresponding quality assurance systems must be provided. The possible applications, effects and limitations of the methods must be recognised as the state of the art on the basis of comprehensive, statistically verified studies and become part of corresponding guidelines. As part of this research project, extensive investigations were carried out into the mode of action and effectiveness of higher-frequency hammering methods. The results of the experimental investigations show that the positive effect of the higher-frequency hammering processes, HiFIT and UIT, is based on the residual compressive stresses and surface layer hardening generated by the plastic deformation of the seam transition. The crack initiation phase is extended and the crack propagation phase is delayed by crack closure effects, so that the experimentally determined fatigue strength is increased by 80 to 100 per cent compared to an untreated weld seam. The same improvement is achieved with pre-damaged but macrocrack-free weld seams. The devices have been optimised for maximum effectiveness, process reliability and practical applicability. The device settings required to achieve process reliability were analysed and defined and a quality assurance concept was developed. This concept requires the creation and certification of process instructions, the organisation of user training courses and tests and the performance of quality controls. The further development of a micro-magnetic measuring system provides a measuring system for testing the use of certified higher-frequency hammering processes for components that deviate from the standard application. Various design concepts were developed based on local concepts for the precise calculation of the service life, verified on the basis of experimental results and finally analysed. As a result, a simplified design concept was developed that enables engineers to design components conservatively. The result of the project is a holistic concept that both ensures quality requirements and provides design specifications. Based on the analysed HiFIT and UIT procedures, a certification procedure was developed. This certification procedure is now available for other procedures in addition to HiFIT and UIT. National and international committees are currently working on implementing the results in guidelines. In future, it will not only be possible to apply these procedures, but also to take them into account in the design within the defined limits. This research and development project no. 02PB2103 was funded by the Federal Ministry of Education and Research (BMBF) as part of the "Research for the production of tomorrow" programme and supervised by the Karlsruhe Project Management Agency (PTKA). The FOS-TA initiated and led the industrial working group. Responsibility for the content of this publication lies with the authors: Versuchsanstalt für Stahl, Holz und Steine, Karlsruher Institut für Technologie (KIT), Karlsruhe; Ingenieursozietät Peil, Ummenhofer und Partner, Karlsruhe; DYNATEC Gesellschaft für CAE und Dynamik mbH, Braunschweig; Kranbau Köthen GmbH, Köthen; LKT Klebtechnik GmbH, Aachen; MAN B&W Diesel Gruppe, Augsburg; Maurer Söhne GmbH & Co. KG, Munich; REpower System AG, Hamburg; Schachtbau Nordhausen GmbH, Nordhausen. This project also received EU-REKA status Authors: T. Ummenhofer, S. Herion, J. Hrabowsky, S. Rack, I. Weich, G. Telljohann, S. Dannemeyer, H. Strohbach, H. Eslami-Chalandar, A. K. Kern, D. Pinkernell, M. Smida, U. Rahlf, B. Senk Publication: 2011